1. Field of Invention
The present invention relates to an illumination device, and more particularly to an illumination device having an expandable structure, which has desirable heat dissipation effects and is easily maintained.
2. Related Art
Currently, a light emitting diode (LED) has already been used on a road lamp for illumination. The LED has advantages of a low power consumption, high luminance, and long lifetime, and thus can solve the problems such as a high power consumption and short lifetime of a conventional mercury road lamp. However, when the LED is applied to the road lamp, the problem of poor heat dissipation still occurs, and the high-temperature heat source generated by the LED causes the heats to be accumulated inside the lamp. As a result, the circuit substrates or electronic devices are damaged due to being overheated.
Therefore, a heat dissipation device is needed to divert the high-temperature heat source generated by the LED out of the lamp, so as to entirely reduce the high-temperature heat energy accumulated inside the lamp, and thus, the LED can operate to emit lights normally at a low temperature. A commonly adopted technical means is to utilize the forced convection principle of an auxiliary fan to generate forced heat exchange convection inside the lamp. The forced heat dissipation by using the auxiliary fan requires opening ventilation holes, so as to realize the purpose of rapid heat dissipation. However, the lifetime of the fan is shortened if it is operated under various severe climatic conditions, such that the cost of the lamp is increased. Moreover, the maintenance and replacement of the fan inside the lamp are rather inconvenient.
Furthermore, in the conventional heat dissipation manner, a heat-sink lamp housing having heat sink fins is manufactured by die casting molding, and the elements such as an LED and the heat-sink lamp housing are enabled to contact each other. Thus, after the heat-sink lamp housing absorbs the heat energy generated by the LED, a natural convection is directly formed by the exposed heat sink fins of the heat-sink lamp housing with the outside air, thereby dissipating the heat energy via the heat sink fins. In such a heat dissipation manner by using the housing, since the heat sink fins are exposed outside the heat-sink lamp housing, the problem of dust accumulation or bird nesting easily occurs, thereby influencing the heat dissipation effect of the natural convection and greatly reducing the heat dissipation effect of the road lamp.
However, in order to increase the heat dissipation area without compromising the structural strength, the heat-sink lamp housing formed through die casting is likely to have defects of an increased weight, restricted form, and difficulties in die sinking. On the other hand, considering the designing flexibility of products, the heat-sink lamp housing formed through die casting has a fixed structure. With such a structural design, the number of light emitting components inside the lamp cannot be increased timely depending upon the demand for the luminance of the lamp, such that the problem of lacking expandability still exists. Consequently, in order to enhance the luminance of the lamp in the heat-sink lamp housing formed through die casting, the entire set of light emitting components inside the lamp unavoidably needs to be replaced.
Therefore, how to effectively improve the air convection structure inside the road lamp and the expandable structure of the lamp is urgently researched by relevant manufacturers in this industry.